The present invention relates generally to a method of exposing photographic medium, and, in particular, a method for fabricating a translucent graded density membrane type medium which may, among other uses, be used for measurement of mechanical motion or displacement.
Such displacement measurement is useful in a number of different environments, including currency dispenser systems. The reliability of currency dispenser systems, such as those employed in remote teller terminals, depends critically on the accuracy in the monitoring of its performance. A unique method of accomplishing the monitoring function is disclosed in the pending application by William R. Horst and Robert H. Granzow, Ser. No. 108,874, which is assigned to the assignee of the present application, and is hereby fully incorporated into this application by reference. Monitoring is achieved in that invention by the use of a translucent graded density medium or filmstrip which is attached to a mechanical arm, which arm is displaced according to the thickness of a bill. The position of the filmstrip causes an analog electrical signal to be generated with an amplitude proportional to the displacement of the arm. Minimal mechanical load and no restraining forces are imposed on the arm, due to the small, lightweight filmstrip and associated optical system. This method provides a very rapid response using a high level TTL compatible signal output.
Other monitoring systems exist which optically detect a transition at the edge of a document when the document reaches a predetermined position, or which sense a detecting member physically traveling to a certain point; these systems seem to operate in a similar manner as the device disclosed in Ser. No. 108,874. However, a major difference lies in the design of the filmstrip and its interaction with the detector unit to provide an analog output signal, rather than a simple binary indication, which signal is relative to the actual physical position of the filmstrip.